This application claims the priority of Korean Patent Application No. 10-2004-0046048, filed on Jun. 21, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a bake system and, more particularly, to a bake system for manufacturing a semiconductor which can distribute the temperature in a substrate evenly in a bake process.
2. Description of the Related Art
In a photolithography process for fabricating a semiconductor, a bake process such as a pre-bake, in which a photoresist is applied on a surface of a wafer and baked, and a post-exposure bake process, in which the photoresist is exposed in a predetermined pattern and baked, is performed.
A bake system that performs the bake process includes a heating plate, on which the wafer is mounted, and a heater installed on the heating plate to heat the wafer. Here, the heating plate and the heater are disposed in a chamber, in which the bake process is performed. Since a gas, such as the air, flows from a side portion of the chamber, passes above the wafer, and is discharged to the outside through an upper portion of the chamber in the bake process, an air flow, which flows from the outer portion of the wafer to a center portion of the wafer, occurs in the chamber. Generally, in the bake process, the temperature should be distributed evenly in the wafer according to a strict temperature deviation standard. For example, the temperature deviation in the wafer should be less than 0.3° C. in the bake process. However, heat convection occurs due to the above air flow, and the temperature at the center portion of the wafer becomes higher than that of the peripheral portion of the wafer. Therefore, even if the heating plate is heated by the heater evenly, the wafer cannot be heated evenly.
FIG. 1 shows a conventional bake system for solving the above problem. Referring to FIG. 1, a cover 62 is disposed on an upper portion of the heating plate 51, on which the wafer W is mounted, and a chamber S, in which the bake process is performed, is formed in the cover 62. In addition, a first heat pipe 73 of a ring shape that surrounds a discharge hole 65 and a second heat pipe 74 of ring shape on an outer portion of the first heat pipe 73 are installed on an upper wall of the cover 62. In addition, an adiabatic member 75 is inserted between the first heat pipe 73 and the second heat pipe 74. An operating liquid is filled in the first and second heat pipes 73 and 74, and the operating liquid transmits the heat through evaporation and condensation to make the temperature of the upper wall of the cover 62 uniform. In the above structure, when a temperature deviation exists on the upper wall of the cover 62 due to the flow of gas that is induced in the chamber S in the bake process, the first and the second heat pipes 73 and 74, which are controlled by a temperature control device 80, make the temperature of the upper wall of the cover 62 uniform.
However, in, the above described bake system, even if the temperature of the upper wall of the cover 62 is uniform, a temperature deviation may still exist in the wafer W due to the flow of gas. In addition, two heat pipes 73 and 74 must be installed on the upper wall of the cover 62, and thus the structure and temperature controlling mechanism of the bake system become complex.